Arbitration - NEC V850ES/KE1+ User Manual

16.11 Arbitration

When several master devices simultaneously generate a start condition (when the IICC0.STT0 bit is set to 1 before
the IICS0.STD0 bit is set to 1), communication among the master devices is performed as the number of clocks is
adjusted until the data differs. This kind of operation is called arbitration.
When one of the master devices loses in arbitration, an arbitration loss flag (IICS0.ALD0 bit) is set (1) via the timing
by which the arbitration loss occurred, and the SCL0 and SDA0 lines are both set for high impedance, which releases
the bus.
The arbitration loss is detected based on the timing of the next interrupt request signal (INTIIC0) (the eighth or ninth
clock, when a stop condition is detected, etc.) and the ALD0 bit = 1 setting that has been made by software.
For details of interrupt request timing, refer to 16.6 I
Master 1
SCL0
SDA0
Master 2
SCL0
SDA0
Transfer lines
SCL0
SDA0
2
CHAPTER 16 I
2
C Interrupt Request Signals (INTIIC0).
Figure 16-11. Arbitration Timing Example
User's Manual U16896EJ2V0UD
C BUS
Hi-Z
Hi-Z
Master 1 loses arbitration
509